Control apparatus



March 23, 1943. 5 PETERSON 2,314,421

CONTROL APPARATUS Filed Aug. 3,1 1940 INVENTOR Aer/we S. five-e50 ATTORNEY Patented Mar. 23, 1943 CONTROL APPARATUS 7 Arthur S. Peterson, Marseille, Ill., assignor to Certain-Teen! Products N. Y., a corporation of Corporation, New York, Maryland Application August 3, 1940, Serial No. 350,247

Claims.

This invention relates to an apparatus for suspending a comminuted solid material in a liquid, especially to the process and apparatus for effecting such suspension in a continuous economical manner. The invention particularly relates to the mixing or incorporation of filler materials, usually of mineral character, in asphalts used for coating sheets of asphalt roofing.

In the production of composition roofing a web of felt, usually containing fibers derived from rags, paper, wood and other cellulosic materials, is saturated with asphalt and thereafter has applied thereto a coating of asphalt. In order to obtain the desired resistance to the weather, heat, moisture and other conditions to which such roofing is subjected and to secure a suitable thickness of the coating on the sheet, it is customary to incorporate in the coating material,

that is, the coating asphalt, a powdered mineral material such as slate flour or ground limestone. These filler materials increase the resistance of the coating to plastic flow when the roofing is laid on the roof and exposed to the heat of the sun and also increase the resistance of the coating to weathering because of the opacity which is added to the coating by these materials. It is an important quality desired in a roofing sheet that means shall be provided to prevent to as 'great a degree as possible the actinic rays of the sun reaching the saturating asphalt carried by the felt, thus to preserve the saturant and the coating from the destructive effects of the rays of the sun and, as well, from the drying out of the protective oils in the saturant.

In many cases asphalt roofings are surfaced with a protective surfacing of comminuted material, such as granular slate, crushed brick, ceramic granules and other types of surfacing materials which also serve to a great extent to prevent the rays of the'sun from reaching the underlying coatingand the saturant therebeheath. In such surfaced roofing sheets it is necessary that the coating shall have proper qualities of adhesion or grip upon the granules applied thereto. This is accomplished in part by providing suitable wetting properties in the adhesive coating material, that is, the asphalt. These properties may be secured and modified by the incorporation of the filler materials above referred to.

In order to control the above-mentioned and other conditions of roofing manufacture it is particularly desirable that the filled coating shall be maintained with a uniformity of mixture,

filler to the asphalt in which it is mixed. The

amount of filler material carried by the filled coating may vary between 25 and 50% but in the usual case about to of the filled coating is" represented by the filler material. In any case variations in the percent of the filler carried by the coating are undesirable because thereby the resistance and other physical qualities above referred to will vary with a resulting unsatisfactory product. Uniformity of mixture assists in insuring that the coated sheet has a coating of uniform quality throughout its extent.

Heretofore it has been the practice to deliver the dry comminuted filler materials and the asphalt coating material to the mixing apparatus manually or with manual control. The intermixing of the filler and the coating then has been carried out as a batch operation. Because of inadequate or inconvenient means of measurement of the quantities of the filler and asphalt delivered to the mixer this batch operation frequently resulted in'non-uniformity of the mix. Moreover, variations in the quality of the mixed product occurred because of variation in 'the completeness of the mixture whichwas effected bysuch a batch operation.

that is, with a uniform ratio of-the comminuted It isan object of the invention to provide apparatus for utilizing it which will secure a continuous supply of intermixed liquid and comminuted material having a uniform quality of mixture.

It is a further object of the invention to provide for variation of the ratio of the comminuted material to the liquid material so as to secure difierent desired mixtures while maintaining substantially continuous operation.

It is a feature of my invention that I provide a positive continuous delivery or feed to the mixing chamber of each of the ingredients of the mix, that is, of the asphalt and of the filler material. Moreover, these materials each are fed in this continuous manner in controlled amounts so that the quantity or the volume thereof is measured and thereby the ratio of one to the other predetermined.

Cooperating with the two means for effecting delivery of the'respective ingredients, namely, the asphalt; and the comminuted material to the mixer, I provide means for varying the rate of delivery of one such delivery means relative to the other. This means for variation of the rela- .tive deliveries may take the form of a power be varied relative to that of the other. A variable speed drive or transmission of conventional design may be used. By virtue of a power means connected to both said delivery means and to said transmission means delivery of the .two ingredients may be effected concomitantly and the rate of one may be adjusted to the desired amount in relation to the rate of the other by varying the adjustment, or setting of the transmission means.

The invention may utilize as part of this apparatus a metering pump or other fluid forcing means for delivery of the asphalt to the mixer from a suitable source containing the asphalt which has been raised in temperature to such an extent'as to provide the necessary fluidity. The apparatus also may include a means, such as a conveyor or other means for transporting solidmaterial, which is of a type which will determine by its rate of operation the amount of material so delivered to the mixer for incorporation in the asphalt.

It is a particular feature of the invention that means are provided for controlling the operation of the means for delivering or feeding the ingredients so that the amount of material being mixed in the mixing chamber shall be main tained within desired limits and that a sufllcient amount of such material shall be acted upon by the mixing device operating within the chamber to secure substantially uniform mixing. The control means is constructed so as to be actuated upon variation in the amount of the material contained within the mixing chamher and acts to control the operation of the respective feeding or delivery means, preferably to initiate their operation substantially simultaneously and likewise to cut off their operation at the same time. In this manner the ratio of the amounts of the materials being delivered or of their volumes may be controlled and the mixing may be carried out continuously. The mixed material may, therefore, be continuously withdrawn from the mixing chamber with the assurance that a uniform mixture shall have been effected because of the requisite delivery in the proper proportions of the ingredient materials made possible under the control of the invention.

Further objects and advantages of my invention will be understood from the following description in connection with the drawing, in which The single figure is a diagrammatic representation of the apparatus of the invention.

' In the figure is shown a mixer I comprising a mixing chamber 3 containing the materials being mixed, and a mixing device, of which the top member or paddle 5 is shown, which may be supported and driven in any suitable manner.

The chamber 3 is provided with an outlet conduit 6 for withdrawal of filled coating therefrom.

Conduit I is connected to a supply of asphalt heated to the proper fluidity for mixing. Metering pump 8 feeds the asphalt from conduit 1 to conduit Ill, through which the asphalt is delivered to the mixing chamber- 3. A suitable metering pump for fluid asphalt in this application is a gear pump which is steam jacketed or otherwise heated to maintain the proper temperature of the fluid asphalt.

A bin or hopper ll containing filler material I2 is provided with a measuring screw feeder l3 driven by sprocket I5 on shaft l4. The discharge of the measuring screw I3 is delivered Sprocket 29 of the variable speed transmission unit 28is connected by chain 24 to drive the sprocket l5on the shaft l4 of filler feed screw l3. ,The ratio of speeds of the sprockets 21 and 29 may be changed and adjusted by adjustment of the hand wheel 25 on the transmission unit 28.

The control apparatus of the invention is generally indicated by the numeral 30 and comprises an inverted air bell 32 having the open end 33 thereof positioned within the chamber 3 adjacent or substantially at or below the level at which, for proper mixing, the fluid asphalt with which the filler is being mixed is to be maintained. A U tube manometer 34 having an open leg 36 and a closed leg 38 is connected to the bell 32 by a pressure transmitting conduit, such as a capillary tube 35, for transmitting the pressure of the air which becomes trapped in bell 32, as the level of the asphalt rises above the lower end of the bell, to the closed leg 38 of the manometer 34. The manometer 34 contains a suitable liquid 31 which may be water, oil or any other fluid which is in substantially stable liquid state at ordinary temperatures.

Positioned in the open leg 36 of the manometer 34 is a float 40 connected by stiflf arched arm 42 to end portion 44 of lever 46. The-lever 48 is pivoted at 48 intermediate the ends 44 and 50 thereof for free movement in the plane of the figure and has mounted for movement along end portion 50 thereof a weight 52. Also mounted upon the lever in a suitable position is a switch 54 which may operate by the tilting of the lever 46. tube having contacts sealed therein and containing a globule of mercury which when the tube is tilted in one position bridges across the contacts and completes the circuit and when the tube is tilted oppositely breaks the circuit. This type of mercury switch is commercially available under the trade-name Mercoid.

The switch 54 is connected in series with the power supply lines 50 and the motor 20 through a suitable control, such as rheostat 52 adjusted by manual control knob 64, for varying the speed of the motor.

The operation of the device shown in the figure is as follows: The paddle 5 of the mixer is kept in constant movement while the roofing machine is being operated. When the quantity of material 4 in the mixer chamber becomes re-. duced, due to withdrawal of filled coating through the conduit 6, the pressure within the air bell 32 and also in capillary tube 35 and closed leg 38 of the manometer decreases, causing the liquid 31 contained in the open leg 36 of the manometer 34 to fall. Float 40 connected by arm 42 to end 44 of lever 45 likewise is lowered and causes the lever 46 to assume a tilt with the end 44 lower than the end 50. With a given adjustment of the parts the mercury switch 54 will be closed by the tilting of the lever 46 when the pressure in the bell 32 has fallen to a certain The switch may comprise a glass as line X-X, of the materials in the mixer.

The circuit through the rheostat 82 to the driv ing motor 20 from the power supply 60 will Both the metering pump 8 and feed screw l3 are positive displacement devices so that for a given rotational movement thereof a predetermined volume or amount of material is delivered to the mixer chamber 3. The ratio of the amount of filler material to the amount of asphalt may be varied at will by means of handwheel 26 on unit 28 which allows adjustment of the rotational speed of the filler measuring feed'screw drive sprocket 29 with respect to the rotational speed of the metering pump sprocket Hi. When, however, the handwheel 26 is properly adjusted to give the desired percentage of filler in the coating it is unnecessary to change the adjustment unless the conditions under which the asphalt and filler are being fed become changed or it is desired to modify the mix.

In order to provide for continuous operation and the continuous control of the mixing of the filler and the coating it is desirable to set the speed of the motor 20 so that the delivery of the filler and of the coating to the mixer chamber 3 will approximate the withdrawal of the filled coating therefrom. If the rate of withdrawal of the filled coating through the conduit 6 exceeds the total quantity of coater and filler received by the chamber 3 from the conduits I and H, the speed of the motor 20 may be manually adjusted by means of knob 64 of rheostat 62 to speed'up the motor 20 and enable it to deliver the materials in amounts approximating the withdrawal. Conversely, with a reduced withdrawal of the filled coating the speed of the motor may be reduced until feed of the materials approximates the withdrawal.

The operation of the control device 30 then may act to maintain the requisite amount of material Within the mixer for proper mixing and with the necessary amount of material overlying the paddle 5. When withdrawal of the filled coating from the mixer ceases or is reduced or for some other reason the level of the materials in the mixer rises, the pressure in the air bell becomes increased, thus raising the height of the liquid in the open leg 36 of the manometer 34 causing float 40 to lift the end 44 of the lever 46. The mercury switch 54 may thus become tilted to its off position thus stopping the motor 20 and feed of the fluid asphalt coating and of the filler to th mixing chamber 3. By suitable adjustment of the parts this action may be made to occur when the level of materials in the mixer has risen to a predetermined line Y-Y. If withdrawal of the filled coating from the mixer chamber 3 continues the level will thereafter fall for the time during which the motor and the feeding means remain stopped. By suitabl adjustment of the parts, as the float 40 falls with the level in the open leg 36 of the manometer, with the fall of the level of the materials in the mixing chamber 3, the switch 54 again becomes tilted to the "011 position with the corresponding starting of the motor and of the coater and filler feeding devices. Thus within limited variation predetermined quantities of filler material and coating are maintained within the mixing chamber for mixing therein. Continuous operation of the mixing device within the chamber 3 upon a substantially constant amount of material thus is insured and uniform mixture thus may be obtained when the quality of the materials as they are delivered to the mixer,-that is, the asphalt and the filler, and the temperatures and other conditions thereof remain, constant.

It is to be understood that suitable heating means, not shown in the figure, may be incorporated in the asphalt feed lines I and I0 and in the metering pump 8 in order to keep the asphalt coating in th liquid state. Likewise means may be provided for heating the mixing chamber 3 and the discharge conduit 6 to prevent the asphalt from solidifying therein.

The remote actuated control device indicated generally at 30, avoids difiicultieswhich, particularly with viscous and solid materials such as asphalt and filler, would be encountered with a conventional float type of level control, in which a float is directly in contact with the liquid to be regulated. If such a conventional float control were to be used in my apparatus the float would soon become weighted down with asphalt accumulated thereon and no longer operate accurately. By using an air bell 32 of suflicient diameter, that is, about 2 to 4" diameter, 1 have found that accumulation of asphalt on the sides of the air bell has a negligible effect on the operation of the level actuated control device of my invention while retaining a sufiicient limitation of the volume of air in the bell for sensitive actu' tion of the device. I

The mounting of the weight 52 for movement along end portion 50 of lever 46 permits adjustment of the height of level desired to be maintained in the filler mixer chamber 3. When the weight 52 is positioned to the left of the position shown in the figure, a lower level will be maintained in the mixer chamber 3 and when to the right of the position shown in the figure a higher level will be maintained. Adjustment of the position of the weight 52 may also be required to compensate for heating of the air within the air bell 32 when the apparatus becomes heated by the hot materials being mixed. Such heating would cause an abnormal increase in pressure in the air bell out of proportion to the height of filled coating in the mixer chamber 3.

The particular embodiment illustrated is an close the electric circuit. Other types of feeding devices for the coating and filler maybe used and the amount of material fed may be determined by other means for example, by valves or separate metering devices rather than by the metering feed device itself.

Having thus described my inventionpI now claim:

1. Apparatus for eflecting suspension of a dry comminuted material in a liquid comprising a mixing chamber, means for positively feeding metered amounts of said liquid and of said cornminuted material to said mixing chamber, continuously acting means within said chamber for effecting intermixture of said liquid and said comminuted material, means connected to said chamber for continuously efiecting withdrawal of the intermixed material therefrom, and control means responsive to variations in the level of material contained in said mixing chamber, said control means being connected to said feeding means to actuate said feeding means substantially simultaneously to initiate said feed of said liquid and of said comminuted material to said mixing chamber when the amount of material being mixed in said chamber falls to a predetermined quantity and to stop said feed when said material within said chamber reaches a predetermined quantity, said control means being ineffective to initiate or stop action of said mixing means.

2. Apparatus for mixing asphalt and a comminuted filler material comprising a mixing chamber, continuously acting means within said chamber for effecting intermixture of fluid asphalt and comminuted filler material fed thereto, a metering pump connected to deliver asphalt from a supply to said chamber, screw feeding means for effecting feed of measured quantities of filler material from a supply to said chamber, power transmission means connected between said metering pump and said screw feeding means, said transmission means being constructed and arranged to be variable at will to change the relative speeds of said metering pump and said screw feeding means, power means connected concomitantly to drive said pump and said screw feeding means, an air bell positioned within said chamber with the open end thereof adjacent the level desired to be maintained in said mixing chamber, and control means operated by the rise and fall of pressure in said air bell upon rise and fall of the level of the materials in said chamber and connected to said power means to actuate said power means to initiate and to stop drive both of said metering pump and said screw feeding means, said control means being ineffective to initiate or stop action of said mixing means. 7

3. Apparatus for mixing a liquid and solid comminuted filler material which comprises a mixing chamber, continuously operating means within said chamber for effecting mixture of said liquid and said filler material, means for dehvering liquid to said mixing chamber, means for delivering filler material to said mixing chamber, power means connected concomitantly to actuate both said delivery means, an air bell having the open end thereof positioned in said chamber adjacent the minimum level of the mixed liquid and filler material within said chamber, means responsive to variations in pressure within said air bell caused by variations in said level of mixed material in said chamber and acting upon said power means to stop and start the same in accordance with the rise and fall of said mixed material in said chamber to stop and initiate delivery of both said liquid and said filler material, said last means being ineffective to stop and start said mixins means, and means for continuously withdrawing from said chamber the liquid and filler materials mixed therein.

4. Apparatus for mixing a liquid and a solid comminuted filler material which comprises a mixing chamber, continuously operating means mounted within the chamber for effecting mi!- ture of said liquid and said filler material, means for delivering the liquid to the mixing chamber, means for delivering the filler material to said mixing chamber, power driven means connected to both said delivery means concomitantly to actuate both said delivery means, means responsive to variations in the level of the materials being mixed in the mixing chamber for controlling said power driven means and thereby to control the delivery both of said liquid and of said filler material to said chamber to maintain therein a predetermined quantity of said materials being mixed, said control means beini! connected to said power driven means to actuate said power driven means independently of said continuously operating mixing means.

5. Apparatus according to claim 4 which comprises means operable at will connected to both said delivery means for varying the ratio of the amounts of said liquid and of said comminuted filler material delivered to said chamber.

ARTHUR S. PETERSON. 

